This invention relates generally to an improved tone arm for record players, and more particularly concerns an articulated tone arm which permits improved tracking of the stylus in a record groove and which has an improved suspension system, whereby tracking error during record play is reduced to zero, and whereby frictional forces in the arm are greatly reduced.
It is well known that the quality of reproduction of a record is affected by the "tracking error" of the tone arm as the stylus follows the groove of a record. A record groove carries lateral vibrations that should move the stylus back and forth at right angles to the groove. As the groove is a very slight spiral, and thus almost a perfect circle, with its center corresponding with the center of the disc, the stylus should move back and forth along a radius from the record's center. Any deviation from this radial vibration of the stylus is known as tracking error. The result is distortion and unpleasant noise in the reproduced sound, as well as increased record wear.
To reproduce the information recorded on a record, a tone arm is conventionally pivotally mounted at a fixed location upon a chassis adjacent the side of a rotatably mounted turntable. The weight of the tone arm wedges the stylus of a reproducing pick-up assembly into the groove, with the electrical output of the reproducing pick-up being proportional to the lateral displacement of the stylus by the lateral vibration of the groove sides. With such a conventional arrangement, it can be seen that the stylus moves through an arcuate path and thus the vibrations of the stylus are not maintained at right angles to the groove as they should be.
Another problem with conventional tone arms has been skating of the stylus across the record. As a result of the forces exerted on the stylus of such a conventional tone arm during playing of a record, since there is an angle between the line tangent to the groove and the line between the stylus point and the pivot point of the tone arm, there is a component of force directed radially inwardly of the record which tends to pull the stylus towards the center of the record. This radially directed force may cause the stylus to jump over one or more convolutions of the spiral groove in a skating or skipping action.
In order to reduce the tracking error and skating of such conventional tone arms, numerous attempts have been made to ensure that the stylus lies tangentially to a circle centered at the center of the record and thereby vibrates in a radial direction. Suggested solutions can be seen, for example, in U.S. Pat. Nos. 2,522,997 of Coppleman; 2,966,360 of Herve; 3,232,625 of Van Eps; 3,826,505 of Birch; 2,455,529 of Shortt; 2,983,517 of Kline; 3,051,493 of Dreier; 3,502,339 of Tatter et al.; and Canadian Patent No. 582,660 of Burne-Jones. Many of these solutions proposed are cumbersome and expensive to incorporate on a record player. Most of these solutions which suggest articulated tone arms require several pivot points at which frictional forces can be exerted upon the tone arm to reduce its efficiency. These pivot points and sources of friction are necessitated by the very nature of the geometrical solutions to the tracking error and skating problems offered in these prior art solutions.